Process of recovering zinc and other volatile metals.



T. HUNTING"I'ON & F HEB ERLEIN. rnoonss 0F REGOVER I NGZING AND OTHERVOLATILE METALS.

APPLIOA TION FILED 001.25, i910.-

1&069085, Patented July 29, 1913.

' WITNESSES:

a i Y r r ATTERNEYS. k

UNITED STATES PATENT OFFICE.

u'nonxs mm'imo'ron, or ennon, ENGLAND, Ann mammal: rmnnnmam,

-- rmnxron'r-on-rnn-uam, ennmanr.

rnocnss or moon-mine znwann ornnn-vom'rrm METALS.

Savignystrasse, Frankfort on the Main, Germany, have lnvented certainnew and useful Improvements in Processes of Recoverin Zinc and otherVolatile Metals, of

which the following is a full and exact specification. Owing to thedeficiencies of the processes in general use up to now for thedistillation of zinc ores in muffle furnaces, efforts,

have been made with a view of carrying out the zinc distillation inshaft blast furnaces, but-all such trials have been-unsuccessful. Thefailures are mainly due to the working of the blast furnace itself.Owing to the complete liquefaction of the slag and to the continuity ofthe process, it is found impossible to keep the escaping gasessufiiciently free from oxygen contained in the air blast and alsofromother oxidizing gases, (carbon dioxid, CO and the like), the

presence of such oxidizing gases making it impossible to obtain the zincvapors free from oxid and to then condense them into a compact metal. Itis for these reasons that thus far only zinc oxid or zinc dustcontaining a high percentage of zinc oxid have been obtainedin blastfurnaces.

The presentinvention has for zinc in a compact metallic form by means ofa process in which air is blown through muffle residues.

the mass of ore. I

The invention is based on a well known process, the object of which isto volatilize the zinc and to recover it in the form of zinc oxid. Thisknown process. consists in mixing zinc ores or 'zinkiferous products ina pulverulent or granular-form with fine coal or other fuel when notalready contained therein, n-sfor instance in the case of The mixture isthen fed into a suitable furnace, such as for instance theHuntingtcn-Heberlein converter furnace, and after starting ignition,submitting it to the action of a current air traversing the layer ofmaterial under treatment from below up to the surface of the charge.Owing to the phenomena of combustion,

Specification of Letters Patent. Application filed October 25, 1910.Serial 110. 589,082.

- v vent-ion this known an its object' blowing process is modified nsucha way the solving of the problem of recovering reduction andoxidation which take place, the zinc is volatilized and carried along inthe form of oxid together with the escapmg combustion gases and is thenrecovered by' means of suitable filterin devices or the like. After the'more or ess perfect removal of the zinc from the charge, a sintering ofthe furnace contents takes place and the process is thus finished. Thesintered residues are then discharged, for instance by tilting theconverter and the furnace is then fed with a fresh charge. Contrary tothe blast furnace work, the process therefore is a discontinuous one.

In the process just described, as well as in other similarvolatilization recesses where the air current is directed low to thetop, the intention and result was always to recover the zinc in form ofoxid. The methodwas either to employ a relatively thin layer of materialin connection with a relatively low air pressure or a relatively thicklayer with a relatively high air pressure. In both cases the gasesalways contained oxygen and other oxidizing gases (carbon dioxid and thelike) in excess and the nascent zinc va rs therefore were con vertedinto oxid. n all these known processes it is neither intended nor is itossible to recover the zinc in aliquid metallic form,

rem bepatented July 29,191abecause thepresence of anexcess of oxygen,

and otheroxidizing gases is thereby in-' ,evitable. No'w accordln to thepresent in that the air and gas current is not directed from below tothe top but reversed, namely from the'surface of the charge through itto the bottom, the layer of charge being comparatively thick. In thecourse of trials carried out with .these new methods, the startlingresult was observed, that oxidation of the zinc vapors can be avoided,so that thesevaP rs 'on leaving the charge may be almost completelycondensed and liquefied by suitable means and thus be recovered in acompact metallic state.

In the accompanying drawing illustrating a furnace adapted forperforming the process in accordance with our invention a is a converterfurnace filled with the charge a resting on the perforated grate f,while cl is 'a cover tightly secured upon the converter and providedwith an air inlet 6. The out-v let for the gases and vapors is'at g. The

discontinuous air Converter can be-ti'lted over by turning the trunnionse on which it is supported.

The process may be carried out for instance as follows: The zinkifero'usore or zinc products mixed with fuel is fed in a comparatively thicklayer into a converter furnace. ()n the surface of the charge anignition fire'is started and through theair-tight converter-hood acurrent of air is admitted. First a combustion of the fuel will takeplace in the upper part of'the layer, and

owing to the increase of temperature therebycaused, and also owing tothe reaction of the ore-particles with the carbon present in the mixtureand the carbon mo-noxid developed by the combustion, the zinc willhereduced in this upper layer and will pass vertically downward in formof metallic vapor together with the gas. current. The gases "comingfromthe upper layers will grad. ually preheat the mixture of ore' and.coalbelow., After some time, the whole'fuel of the upper layer willbe'burned. out bringing the temperature in this layer to such a degree,that the mass is sintered. In the meantime, the zinc fromthis upperlayer has dis-' tilled out, the completeness of its removal beingconsiderably furthered by the close contact existing'in the moment ofsintering between the coal still present in the charge, and the oreparticles. Through the sintered upper layer which is screen-likeinterspersed with air-ch'annels,-the fresh air current is passing andreaches the lower unsintered layer, which still contains the bulk of itsfuel-contents. The same phenomenon as in the uppermost layerwill nowtake place here, i. e. the fuel will be burnedby the oxy-' gen of theairand theKzi-nc volatilized, until finally the sintering of the wholemass is accomplished. These phenomena will continue downward from onelayer to the other, until the sinte-ring zone has reached the bottompart of the charge, when the process is finished. The gases andmetahvapors escaping .from the layer'which is near the sintering state,pass through the layers lying beneath until they escape at the bottom ofthe charge. Thus the gases Will preheat these layers of charge andprepare them, by. reducing and decomposing the oxids; carbonates,sulfates and like compounds contained in the charge and injurious tothesubsequent production of metallic zinc vapors. On the other hand,

oxidizing constituents of the gases will be reduced in passing throughthe still unsintered layers of the charge intermingled with live coal,so that on leaving the charge at the bottom, the gases essentiallyconsist of only carbon monoxid (CO) and nitrogen.

The zinc vapors mixed with thegases will first be partly oxidized andretained in the charge in the form of zinc oxid, and partly condenseditoa metallic state in the inferior cooler layers of the charge. During acercar'ry along the carbon monoxid and the oxitain preliminary stage ofthe operation,

which according to the prevailing conditions I will be shorter orlonger, no zinc vapors will thus escape from the lower part of thecharge, but only the gases developed by the combustion of the carbon andthe decomposi tion of the carbonates, sulfates, etc; as soon however asa sufiiciently high temperature is reached also in the lower layers ofthe charge, the principal stage of the process begins, during which alsothe zinc vapors will escape and may be condensed after having left thecharge, by suitable. means, for in;

stance by .causing the gases to pass over cooled surfaces. Owing to theworking of the charge in the preliminary stage and also to the reductionof the carbonic dioxid (CO contained in the gases, by'the incan descentcoal of the charge, the gases are absolutely clean,'and. consistessentially of only \monoxid. of carbon and nitrogen, the condensationof the zinc vapors to liquid. (or solid) metallic" zinc is obtainedwithout diifi culty and the formationof zinc dust and zinc oxid avoided.The astonishing phenomenon is, that in the process described the zincdoes not escape from the charge in the form of zinc oxid, but mainly in.the form of metallic zinc vapors, capable of being condensed to liquidmetallic zinc, whereas in the hitherto known analogous processes and inthe known blast furnace work, only zinc. oxid could be obtained,'o'runder most favorable, circumstances an inferior quality of zinc dust.This is most probably due to the.

following reasons: .When in the process,

where an air current passes through the charge sintering the same, andthe current is directed from the bottom to the top, it is not possibleto obtain,.a uniform distribution of the-air over the whole area of thecharge.

In consequence of their tendency to expand, the gases are seeking apassage throughthc charge at those'points, which otter the leastresistance. Thu's crater-like channelswill be formed in some parts ofthe charge and through these'channels the air reaches the surface of thecharge in a more or less unaltered condition, mixing there with thegases and. vapors escapin from the charge. In addition, thiscrater-formation causes an irregular combustion and sintering to' takeplace, so that, the-sintering-does not propagate upwardly by uniformlayers, but irregularly with respect to the horizontal and verticalsection of the mass. Furthermore,

I the above-mentioned preparatory preheating and reduction is preventedand there are many parts of the mass in which the volatilization of thezinc is taking place simultaneously with the reduction of theabovementioned injurious oxids, sulfates, carbonthat the gases holdingthe zinc vapors also ates, and like compounds, with the result d-izinelements (carbon dioxid, etc.) generated y the reduction of the oxids,sulfates, carbonates, etc., whereby the zinc vapors are converted tooxid. The word oxidizing is used herein the sense that the elements generated by the reduction of oxids, sulfates,

carbonates, and like compounds exert an oxid'izing action upon thezrncvapors. If however according to the present invention, the

s and air current is directed from the surace of the charge downward,and a relatively high layer of charge used, the expansion of the gascurrent is counteracted by the fact of the resistance offered by. the

charge tothe assage of the gases which increasestowar the bottom-inconsequence of the greater density .of the lower layers of the chargeAndthis will have for effect that the gas current is distributeduniformly over 20 the whole area of the charge and crater-likeformations are avoided, hence a uniform preparation of the charge and auniform propagation'of the sintering toward the bottom will take place.And hereby again it is possible to have the escaping gases contain onlycarbon monoxid and vapors of metallic zmc.

From the foregoing it is, obvious that the success of the inventiondepends upon using relatively thick layers of charge, a rela'- tivelythick layer meaning aheight of for instance 100 centimeters. If thelayer is too thin, there will be no preparatory reduction anddecomposition of the oxids, sulfates, carbonates, etc., nor will thegases be cleaned" from oxidizing constituents, which according to theabove explanations, is indispensable for obtaining condensable metalliczinc vapors. The height of layer required for each case however dependsupon the percentage of zinc and the nature of the material to betreated,and must be established for each material by practical experience.

It is evident that the pressure and quantity of the air passing throughthe mass must be proportionate, that isto say adapted to the height oflayer employed and other prevailing circumstances. Pure oxygen ora'irenriched in oxygen or preheated air or oxygen may of course be employedinstead of air/ In: workiiigathelpiocess practically, it was found thatit was difiicult to distil the zinc out of the lower layers of thecharge in a metallic form, which difliculty may be ex-' plained by thefact that the bottom layer of the charge does not exert asuflicientreducing action upon the'combustion gases and zinc vapors prior to theirescape from the charge. To avoid this difficulty it is advis-- able -toadd in the bottom layer of the charge a larger quantity of reducing fuelthan in the rest of the charge. Owing to this in crease of reducing fuelin the lower layer, the dangerof reoxidation of the zinc vapors islessened and it is possible to distil the zinc in metallic form also outof the lower layers of the charge. Itmight be advisable to'have no oreat all in the bottom layer ofthe furnace, but to allow the charge torest upon a layer of reducing fuel (preferably coke). This reducingbottom layer might serve as a grate, by putting for instance on thebottom of the furnace first a la-yer of coarse coke, and upon thisalayer of finer coke, upon which-the charge itself 'is fed. It mightalso be advisable to separate the charge into several layers and providea layer of charge richer in fuel (or of fuel only) between two suchlayers. The arrangement of layers of higher reducing capacity between orun..lcrneath the charge may have another favorable effect, inasmuch asthese layers. secure, during the whole operation, a more perfectreduction of the oxidizing constituents of the'gases and of the alreadygenerated metallic oxid.

From the process of distilling zinc in blast fu1-naces,;w-l1icl1 neverhas been successful, the present'gprocess differs substantially in that('1) iii'Lt-he present processthe slag is not converted into a fluidstate, but' only sinterecl; (2) the present process is not carried. outcontinuously, but discontinuously, 27. c. in each operation a determinedquantity of charge is submitted to distillation and when completed thework begins once again. As in the well-known blast-furnace distil lationthe zone at which the slag is liquefied must nearly coincide with thezone at which the generation and distillation of the zinc takes place,it is inevitable thatpart of the air blown in or the carbon dioxidgenerated by the combustion, reaches the zinc distillation zone andthereby reoxidizes the zinc vapors. Moreover, in the blast furnaceworlgthere is not suflicient preparation of the charge, '5. c. injuriousoxids, carbonates, sulfates, etc., are not sufficiently reduced anddecomposed before zinc reduction is taking place and because in blastfurnace the layers are naturally charged loosely, the gases traversethem quickly and without the necessary close contact with the particlesof the charge.

The startling result obtained by the present invention, in recovering ina metallic state the zinc vapors on their leaving the charge, may partlybe ascribed to the factthat the charge forms a densely stratified mass,the mass of material being a pulverulent or granular state. or when inform of briquets, 'the spaces between the briquets must be completelyfilled in with fine coal or fine charge material. The thus obtaineddensitv of the charge will further the uniformity of the gasdistribution, and a more intimate contact of thegases with the particlesof the charge, and also will slacken the passage of the gas currentthrough the mass of the charge, whereby a uniform and tained.

'WVOIlU-Bd with profit on materials poor in efficacious The trials onwhich the present invention 1s based, were carried out in a converterfurnace, such as is ma'deu se of in the Huntlngton-Heberleln' process,for roastinglead ores. The converter, and consequently the chargecontained therein, was tapered toward the bottom and it appears thatthis tapering form of, thecharge is of a certain importance for thesuccess of the invention, especial-1y for the purpose of producing cleanmetallic zinc vapors. sequence of this downward tapered section ofdischarge, the uniformity of the gas distribution is furthered, and-thecraterformation counteracted, a better preparation ofthe charge issecured and a better cleaning of the gases, inasmuch as the downwardpassing gases are coming into more intimate contact with the charge inthe lower reduced section of the furnace. Furthermore it-has been found-in thepractical working of the invention, that a certain amount ofwater or other vaporizable liquid in the charge exerts a favorableinfluence upon the course of the process. It would seem that owing tosuch water contents the preliminarylperiod, during which the charge isbeing gradually brought to the rolatilization temperature of the zinc,and prepared in other respects, is extended, and that in the mass of thecharge a system of fine channels is formed by the, escaping watervapors. The volatilization temperature is thereby distributed withgreater uniformity over the whole mass of the charge. Moreover, thefavorable effect of the water is perhaps due to certain chemicalreactions of the water (formation of hydrogen, decomposition of.

injurious compounds, etc). In. comparison with the present zincdistillation processes in muffie furnaces, the present process'has theadvantage of much greater cheapness and .very simplified working.Moreover the new process can be zinc, such as for instance in the caseof retort residues and ore-talllngs, low grade zinc ores and the like. Afurther advantageof the present invention consists in the facti that thezinc recovery-is a good one Doubtnot necessarily confined to theproduction of'me'tallic zinc. In making 'use of the methodscharacterizing the process, zinc may also be recovered in form of oxid,if the zinc-vapors after hav ng escaped from the charge, are allowed tocome in contact with air and thereby burned tooXid.

The invention is not only applicable to zinc, but also to othervolatilizable meta-ls,

preparation of the charge is ob- Because in consively throughout thelower portions of the charge, the metal having the lowest tem per-atureof volatilization first passes from the furnace as a vapor, and then themetal having the next higher temperature of volatilization passes fromthe furnace, and so on. If, for instance, zinc and lead are mixedtogether in the charge, substantially all the zinc vapor escapes first,and then, after the bulk of zinc is volatilized, the lead .vapor startsto pass from the furnace, so

that the two may be recovered separately, as, for example, by directingthe zinc vapors into one place and then diverting'the following vaporsinto another place at the time that the lead starts to volatilize; or,as an. alternative. to the procedure in this example, the. air currentmay be shut off and the-process terminated after the volatilization ofthe zinc is completed. The residue from which the zinc content has beenextracted then remaining in the furnace, may be treated in a blastfurnace for recovering the lead content. Easily volatilized metals, suchas arsenic, antimony, mercury, already escape priorto thevolatilization, of the zinc and may also be recovered separatelyifdesired; la ing thus described our invention whatwe claim as new anddesire to secure by, Letters Patent, is:

LflQhe process of recovering zinc and other volatile metals fromores orother mareducing, decomposing and reducing by said downward escapingcombustion gases the compounds of the charge which may be injurie-ustoth'e subsequent production of metallie vapors, reducing the oxidizingconstituents of the gas current by the incandescent fuel, distillingthevolatile metals out of the charge, condensing the metallic vapors,sintering substantially the entire residues and discharging the sinteredmass.

for preparing the furnace to receive-a fresh charge.

2. The process for recovering zinc and other volatile metals from oresor other materials, which consists in charging a comcompounds of thecharge which may be injurious to the subsequent production of me tallicvapors, reducing the oxidizing constituents of the gate current by theincandescent fuel, distilling the volatile metals cutof the charge,condensing the'metallic vapors, sintering the residues and dischargifresh charge. 1

ing them for preparing the furnace to receive a fresh charge.

3. The process of recovering zinc and other volatile metals from ores orother materials, which consists in charging a comparatively thick layerof the ore-or other material mixed with reducing fuel and moistened witha vaporizable liquid, into a suitable furnace, igniting the charge atthe top,

forcing an air current downward throu h the charge, decomposing andreducing hy the downward escaping combustion gases the compounds of thecharge which may be injurious to the subsequent production of metallicvapors, reducing the oxidizing con- I stituents of the gas current bythe incandescent fuel, distilling the volatile metals out of the charge,condensing the metallic va- )ors sinterin the residues and discharginthem for preparing the furnace to receive a i. The process of recoveringzinc and other volat le metals from ores or other materials, whichconsists in charging a comparativelj thick layer of the ore or othermaterial mixed with reducing fuel into a suitable furnace and uponlayers of in creased reducing power, igniting the charge at the top,forming an air c urrent'downward through the charge, decomposing andreducing by thc downward escaping combustion gases the compounds of thecharge which may be injurious to the subsequent production ofmetallic'vapors, reducing the oxidizing constituents of the gas currentby the incandescent fuel, distilling the volatile metals out of thecharge, condensing the metallic vapors, sintering the residues anddischarging them for preparing the furnace to receive a fresh charge.

5. The process of recovering zinc and other volatile metals from ores orother ma-. terials, which consists in charging a comparatively thicklayer of the ore or other material mixed with reducing fuel into asuitable furnace and upon layers of fuel, igniting the charge atthe-top, forcing an air current downward through the charge, decomposingand reducing by the downward escaping combustion gases the compounds ofthe charge which may be injurious to the subsequent production ofmetallic vapors, reducing the oxidizing constituents of the gas currentby the incandescent fuel, distilling the volatile metals out of thecharge, condensing the metallic vapors, .sintering the residues anddischarging them for preparing the furnace to receive a fresh charge.

6. The process of recovering zinc and other volatile metals from ores orother materials, which consists in charging a com paratively thick layerof the ore or other material mixed wit-h fuel and moistened with'water,into a converter furnace tapered toward the bottom, and upon layers ofincreased reducing power, igniting the charge at the top, forcing an aircurrent downward through the charge, decomposing and reducing' by thedownward escaping gases of 1 sintering the residues and dischargingthem,

for preparing the furnace to receive a fresh charge. r

w 'Lfljlie process of treating ores or other materials containing zincand other volatile metals, which consists in charging a comparativelythick layer of the ore or other material mixed with fuel into a suitablefur,- nace, igniting the charge at the top, forcing an air currentdownward through the charge, decomposing and reducing by',.the downwardescaping combustion gases the compounds of the charge which may beinjurious to the subsequent production of metallic vapors, reducing theoxidizing constituents of the gas current by the 1ncandescent fuel,distilling the volatile metals out of the charge, burning the metallicvapors to .oxid after-they have left the charge,

downward escaping combustion gases the compounds of the charge which maybe injurious to the subsequent production of metallic vapors, reducingthe oxidizing constituents of'the as current by the incandescent fuel,distilling one or more of the volatile metals out of the charge andleaving behind in the residues the other less volatile metals,condensing the metallic vapors, sintering substantially the entireresidues and discharging thesintered mass for preparing the furnace toreceive a 'fresh charge.

9. Theprocess of recovering zinc and other Volatile metals from oresor'otherma- 5 terials, which consists in charging a comparatively thicklayer of the vore or other material mixed with fuel into a suitablefurnace, ignitingthecharge at the top, forcing an air current downwardthrough the 10 charge, decomposing, and reducing by the "downwardescapiitg combustion gases and the compounds of the charge which may beinjurious to the subsequent production of metallic vapors, reducing theoxidizing con 15 stituents of the. gas current by the incandescent fuel,distilling the volatile metals one after the other; out of the charge,con densing separately the different metallic vapors, sinte'ring theresidues and discharging them for preparing the furnace to receive a 20fresh charge.

In testimony whereof we havensigned our names to this specification inthe presence of two subscribing witnesses.

THO As HUNTINGTON; I I FERDINAND HEBERLEIN.

'l/Vitnesses:

JEAN GRUND, CARL GRUND.

Glipies of this patent may be obtained for fivejc'ents each, byaddressing the Commissioner of Patents 1 Washingtom). c.

It hereby certified that int Letters Patent No. 1,069,085, granted July29, 1913, upon the application of Thomas Huntington, of London, IEngland, and Ferdinand Heberlein, ot Frankfort-on-the-li/liain, Germany,for an improvement in "fPro cesses of Recovering Zinc and other VolatileMetals, an error appears in v the printed specitic-ation requiringcorrection as follows: Page 5, line 43, for the word. forming?readforcing; and that the said Letters Patent" should be read with thiscorrection I therein that the same may conform to the record of the casethe Patent Qtfice.

Signed and sealed this 7th day of October, A. D., 191 3. d

R. T. FRAZIER,

Acting Commissioner of lqtents.

discharging thesintered mass for preparing the furnace to receive a'fresh charge.

9. Theprocess of recovering zinc and other Volatile metals from oresor'otherma- 5 terials, which consists in charging a comparatively thicklayer of the vore or other material mixed with fuel into a suitablefurnace, ignitingthecharge at the top, forcing an air current downwardthrough the 10 charge, decomposing, and reducing by the "downwardescapiitg combustion gases and the compounds of the charge which may beinjurious to the subsequent production of metallic vapors, reducing theoxidizing con 15 stituents of the. gas current by the incandescent fuel,distilling the volatile metals one after the other; out of the charge,con densing separately the different metallic vapors, sinte'ring theresidues and discharging them for preparing the furnace to receive a 20fresh charge.

In testimony whereof we havensigned our names to this specification inthe presence of two subscribing witnesses.

THO As HUNTINGTON; I I FERDINAND HEBERLEIN.

'l/Vitnesses:

JEAN GRUND, CARL GRUND.

Glipies of this patent may be obtained for fivejc'ents each, byaddressing the Commissioner of Patents 1 Washingtom). c.

It hereby certified that int Letters Patent No. 1,069,085, granted July29, 1913, upon the application of Thomas Huntington, of London, IEngland, and Ferdinand Heberlein, ot Frankfort-on-the-li/liain, Germany,for an improvement in "fPro cesses of Recovering Zinc and other VolatileMetals, an error appears in v the printed specitic-ation requiringcorrection as follows: Page 5, line 43, for the word. forming?readforcing; and that the said Letters Patent" should be read with thiscorrection I therein that the same may conform to the record of the casethe Patent Qtfice.

Signed and sealed this 7th day of October, A. D., 191 3. d

R. T. FRAZIER,

Acting Commissioner of lqtents.

